A plasma display panel (hereinafter, referred to as “PDP”) is composed of a front plate and a rear plate. The front plate includes: a glass substrate; display electrodes formed on one of the main surfaces of the glass substrate; a dielectric layer covering the display electrodes, which serves as a capacitor; and a protective layer formed on the dielectric layer, which is composed of magnesium oxide (MgO). On the other hand, the rear plate includes: a glass substrate; data electrodes formed on one of the main surfaces of the glass substrate; an underlying dielectric layer covering the data electrodes; barrier ribs formed on the underlying dielectric layer; and phosphor layers formed between the barrier ribs, which each emit light of red, green, or blue.
The front plate and rear plate are hermetically sealed, with their electrode-formed-surface sides being opposed to one another. In discharge spaces which are partitioned by the barrier ribs, a discharge gas containing neon (Ne) and xenon (Xe) is enclosed. The discharge gas produces discharges by video signal voltages which are selectively applied to the display electrodes. The discharges generate ultraviolet rays which excite each of the phosphor layers. Each of the excited phosphor layers emits light of red, green, or blue. Thus, the PDP provides displays of color images (see, Patent Literature 1).
The protective layer has four major functions: the first is to protect the dielectric layer from ion bombardment caused by the discharges; the second is to emit initial-electrons for generating data discharges; the third is to retain charges for generating the discharges; and the fourth is to emit secondary-electrons during sustain discharges. The protection of the dielectric layer from ion bombardment can inhibit an increase in discharge voltage. An increase in the number of emitted initial-electrons can reduce data-misdischarges that may cause flicker of an image. An improvement of charge-retention performance can make applied voltages be reduced. An increase in the number of emitted secondary-electrons can make a sustain discharge voltage be reduced. In order to increase the number of emitted initial-electrons, attempts have been made which include, for example, an addition of silicon (Si) and/or aluminum (Al) to MgO of a protective layer (see Patent Literatures 1, 2, 3, 4, and 5, for example).